An industrial gas turbine includes a combustor formed by a circular array of combustion chambers, which are also referred to as combustion cans. Each chamber has an end cover that includes openings which receive fuel nozzles that extend into a combustion zone internal to the chamber. The fuel nozzles must be securely seated in the openings in the combustion end covers to prevent leakage of hot combustion gases formed in the combustion zone.
Hot combustion gases, other fluids and vibrations in the gas turbine can cause wear and cracking to occur in the openings of the end covers. Wear on and cracking of the opening tends to occur where surfaces of the fuel nozzle abut interior surfaces of the opening. Wear and cracking of the interior surfaces of the opening that abut the fuel nozzle assembly can create gaps between the surface of the opening and the fuel nozzles. These gaps may allow combustion gases to leak through the end cover and mix with other gases flowing to the combustion can or to the atmospheric air.
To address the wear and cracking that occurs on their openings, end covers are periodically removed, such as every few years, from the combustion cans and the fuel nozzles are removed from the openings. The removed end covers are inspected and repaired.
Repair of the openings in the end cover includes adding replacement metal to the interior surfaces of the opening by manually brazing or welding metal inserts to those surfaces. Welding the inserts to the openings is described in U.S. Patent Application Publication 2016/0003479. The inserts and interior surfaces of the openings are machined to return the openings to their design dimensions. Manual welding and brazing of inserts is prone to human error and is time consuming.
While the end covers are removed, the gas turbine is shut down and does not generate power. Substantial costs are incurred due to the loss of power generation and the repair of the end covers, while a gas turbine and the end cover is repaired. To reduce the costs due to the repair of end covers, there is a long felt need to expedite the repair of end covers.